From: Patrick McHardy <kaber@trash.net>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Kernel Netdev Mailing List <netdev@vger.kernel.org>
Subject: Re: [XFRM]: Improve MTU estimation
Date: Fri, 04 Aug 2006 13:11:19 +0200 [thread overview]
Message-ID: <44D32B57.2000304@trash.net> (raw)
In-Reply-To: <20060804101345.GA17583@gondor.apana.org.au>
Herbert Xu wrote:
> On Fri, Aug 04, 2006 at 12:09:18PM +0200, Patrick McHardy wrote:
>
>>I was wondering why the old code distinguished between transport mode
>>and tunnel mode, I couldn't spot anything that would be affected. I'll
>>look into the transport mode case again.
>
>
> The problem is basically you don't know a priori the size of the IP
> options. So you assume the worst case where the IP options causes
> the largest amount of padding for encryption (IP option length itself
> must be a multiple of 4, so for a block size of 8 the worst is 4,
> and the worst is 12 for a block size of 16).
>
> Of course it gets hairier if you have ESP padding. I'm not even sure
> if the current code gets that right.
Unless I'm missing something, the padding caused by IP options
is always less than the worst case that can happen anyway
(max(block size, padlen)-1), so it can simply be ignored.
next prev parent reply other threads:[~2006-08-04 11:13 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-08-04 8:50 [XFRM]: Improve MTU estimation Patrick McHardy
2006-08-04 9:27 ` Patrick McHardy
2006-08-04 10:01 ` Herbert Xu
2006-08-04 10:09 ` Patrick McHardy
2006-08-04 10:13 ` Herbert Xu
2006-08-04 11:11 ` Patrick McHardy [this message]
2006-08-04 11:16 ` Herbert Xu
2006-08-04 11:21 ` Patrick McHardy
2006-08-04 11:25 ` Herbert Xu
2006-08-04 11:50 ` Patrick McHardy
2006-08-04 11:51 ` Patrick McHardy
2006-08-04 11:55 ` Herbert Xu
2006-08-04 11:54 ` Herbert Xu
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=44D32B57.2000304@trash.net \
--to=kaber@trash.net \
--cc=herbert@gondor.apana.org.au \
--cc=netdev@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).